1. Field of the Invention
The present invention generally relates to gear systems and derraileurs for mechanical systems such as bicycles, unicycles, reciprocating engines, reciprocating air pumps, other devices in which varying amounts of pressure are applied thereto, etc.), and more specifically to adjustable variable length bicycle/unicycle pedal crank for gearless shifting.
2. Description of the Related Art
Conventional systems utilize gear systems that are mechanically complex, vulnerable to damage and difficult to adjust and maintain. Additionally, in the case of bicycles, for messengers and other professionals who rely on manually-operated, wheeled vehicles such as bicycles, fancy gear mechanisms increase the attractiveness to thieves and the possibility of theft. It is noted that in bicycle applications the user is a cybernetic factor who determines how much stroke the user desires depending on the load to the user""s legs.
However, despite occasional fads like xe2x80x9cScorchersxe2x80x9d (e.g., one-speed bikes with no coast mechanism), one-speed bicycles have limited utility. The pedal-towheel rotation ratio on a one-speed bicycle must be optimized for slow speeds and traveling up-hill. When the speed increases and the legs move in the full pedal circle at high speeds, ergonomic efficiency drops dramatically. This has been problematic in the past, and thus has limited one-speed cycles"" popularity.
Similarly for air pumps, a long-stroke pump may be needed for high volume, low pressure applications such as for an air mattress, whereas a short-stroke pump may be required for low volume, high pressure applications such as for a tire. This is inconvenient and no efficient, dual-purpose pump for applying varying amounts of pressure has been provided hitherto the invention.
In view of the foregoing problems of the conventional structures, an object of the present invention is to provide, in the case of a bicycle application, a structure for providing a real-time, continuous adjustability to the stroke length of the pedal crank, regardless of low speeds or high speeds of the bicycle.
In a first aspect, an apparatus for gearless shifting, includes a pedal crank; and a pedal arm assembly for telescoping to adjust a length of the pedal crank, to continuously adjust a stroke length of the pedal crank.
With the invention, at low speeds (e.g., low in regard to the desired application), the pedal cranks are fully extended, and maximum leverage is provided for climbing hills and initial pedaling.
At higher speeds, the stroke length can be shortened so that minimal leg motions can be used to continue to apply accelerative force to the drive wheel(s).
When the rider engages the xe2x80x9cupxe2x80x9d cog, a planetary gear (e.g., the drive gear 106 described below) in the pedal crank hub shifts into place which turns an internal shaft which screws the pedal arm into a shortened position.
Likewise, engaging the xe2x80x9cdownxe2x80x9d cog, the internal shaft screws the pedal arm into a lengthened position. Both changes are driven by rotations of the pedal arm assembly (e.g., pedal-powered shifting). Pedal arms are connected together in the hub so that they will extend or shorten in parallel fashion.
The present invention is also applicable to an air pump, and indeed will find great benefit therein. Such an air pump preferably includes a motor, a piston driven by the motor, a cylinder coupled to the piston, and a variable stroke-length apparatus, coupled between the cylinder and the piston, for selectively and controllably adjusting a stroke length of the cylinder.
Thus, with the unique and unobvious features of the invention, a real-time, continuous adjustability to the stroke length of the crank (e.g., pedal crank in the bicycle application) can be provided, regardless of low speeds or high speeds of the bicycle. Further, an air pump may be similarly adjusted.